Update markdownlint-cli container image

[AyobamiH]

Summary

• update the pinned markdownlint-cli container from v0.32.2 to v0.49.1
• retain the immutable image digest pin and move the embedded runtime from Node 16 to Node 24
• preserve the repository's existing lint policy by disabling only rules introduced after the current baseline
• convert two bold monitoring labels into real headings so the existing MD036 rule remains enforced

Why

Issue #315 proposed v0.39.0 in January 2024 to remove the deprecated punycode path. Rechecking that choice now found that the v0.39.0 image embeds Node 20, which reached end of life in April 2026. The current v0.49.1 image embeds Node 24 instead.

v0.49.1 initially exposed two existing MD036 findings in practices/observability.md. Those labels were functioning as headings, so this change converts them to semantic level-three headings rather than disabling MD036. Rules added after the repository's v0.32.2 baseline are explicitly disabled to avoid silently changing the wider lint policy.

Testing

• verified the immutable v0.49.1 digest, CLI version 0.49.1, and embedded Node version 24.18.0
• compared the old and new configurations across every Markdown file: 40 findings before and after, with none added or removed
• confirmed the old image reports the punycode path with pending deprecations enabled, while the new image does not under pending or trace deprecations
• exercised scripts/markdown-check-format.sh through a valid Markdown change and an invalid hard-tab change
• confirmed the invalid change is rejected with MD010
• bash -n scripts/markdown-check-format.sh
• verified a one-commit, two-file diff against current main

Validation: https://github.com/AyobamiH/software-engineering-quality-framework/actions/runs/33161187318

Closes #315

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud